Over-The-Counter Pain Drug May Affect Ability to Empathize

Two experiments tested personal distress and emphatic concern in participants

As well as reducing the pain an individual may be experiencing, acetaminophen may also impede their ability to recognize and empathize with pain in others. Those are the findings of a new study which examined participant's ability to empathize with others after receiving acetaminophen in two randomized, double-blind, parallel-group, placebo-controlled experiments.

In Experiment 1, 40 participants were administered acetaminophen 1000mg in liquid form, while 40 were given placebo. After waiting an hour for the treatment to take effect, the participants read eight short scenarios that described various physical or social pain. They rated perceived pain in two measures; scale from 1 (No pain at all) to 5 (Worst possible pain) and secondly, participants rated on three items how much each protagonist felt hurt, wounded, and pained.

In Experiment 2, 59 participants were administered acetaminophen 1000mg, while 55 were given placebo. The participants were randomized into groups of 4–8 and spent 15 minutes getting to know one another. Three different paradigms were set-up to test for the effect of acetaminophen on empathy. First, participants completed a similar version of the hypothetical scenario measures used in Experiment 1. Second, participants' sensitivity to noise pain and empathy to other's noise pain was measured. And third, empathic responses were measured to actual incidence of social pain.

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Results from Experiment 1 showed that the effect of acetaminophen on perceived social pain was marginally significant. When reading stories of physical pain the acetaminophen group median for personal distress was -0.22 (standard deviation = 1.00) compared to 0.22 (SD=0.82) for the placebo group.

Results from Experiment 2 showed that acetaminophen reduced empathy to an actual incident of social pain, not just one that was read about. In a game (Cyberball) involving three participants, the other participants watched as one participant was ostracized and excluded from playing. The scores for perceived pain, personal distress, and emphatic concern were -0.17, 2.25, and 1.68, respectively for the acetaminophen group, while they were significantly higher in the placebo group, at 0.19, 2.61, and 2.05, respectively.

Acetaminophen is the most common drug ingredient in the U.S., and is the main ingredient of Tylenol. The exact pharmacological mechanism for the lack of empathy is unknown, leading the authors of the study to suggest that their findings underscore the “need for further research on the neurochemical bases of empathy for pain.”

They conclude that, “acetaminophen can also have unappreciated psychosocial side effects by interrupting the fundamental capacity to empathically connect with other people's painful experiences. Quite literally, acetaminophen reduces one's ability to feel another's pain.”